How do I do this on a BA II Plus TI calculator?

Craig's Car Wash Inc. is considering a project that has the following cash flow and cost of capital $($r$)$ data. What is the project's discounted payback? $=2\mathrm{.}09$

Year $0123$

Cash flows $$$$900$ $$500$ $$500$ $$500$ r: $10\mathrm{.}0\%$